DESCRIPTION: Dr. Kernan proposes a molecular and genetic analysis of mechanotransduction in Drosophila. Drosophila external mechanosensory organs exhibit physiological similarities to the vertebrate inner ear. The apical sensory neuronal membranes of insect sensory bristles, like vertebrate cochlear hair cells, are in contact with potassium rich extracellular fluid secreted by the socket cells. Ion-pumping activity sustains a transepithelial potential across this membrane and the mechanical stimulation of the bristle induces current flow into the sensory neuron. Previously, Dr. Kernan identified five genes that exhibited a touch- insensitive phenotype from a mutagenesis screen of the X-chromosome. Two of these genes, unc and uncl, exhibit defective mechanoreceptor potentials without any apparent defects in the morphogenesis of bristles or sensory support cells. More recently Dr. Kernan has screened for mutations mapping to the second chromosome which exhibited severe adult uncoordination. Seven complementation groups were identified and these genes will be studied further with respect to their electrophysiology. Dr. Kernan proposes to complete the screen for putative mechanosensory genes by a mutational analysis of the third chromosome. Initially, mutants will be screened based upon their non-motility during late pharate development and subsequently uncoordinated behavior at the adult stage. Following standard complementation and mapping experiments, the mutants will be subjected to electrophysiological analysis to assess transepithelial, mechanoreceptor, and action potentials. The sensory organs of the isolated mutants will be examined for developmental defects by a combination of microscopy and cell marker studies. Dr. Kernan is specifically interested in genes which directly affect mechanoreceptor function as opposed to genes responsible for the development of the structure of the sensory organs. Dr. Kernan proposes to complete the molecular cloning and characterization of the unc and uncl genes. P-element-mediated rescue of the mutant phenotype will be used to determine the identity of the clones. He also proposes to clone the autosomal mechanosensory genes; a P-element tagging strategy may be used to facilitate their identification. Once the genes have been cloned, antibodies for their gene products will be reared and used for analyzing tissue and cell specificity of expression.